As is well known in the art, mobile radio systems, such as cellular telephone systems, employ a number of geographically-spread base transceiver stations with which mobile stations, such as cellular telephones, can communicate by radio. Typically, while a mobile station is switched on, the system keeps track of the area in which the mobile station is situated, that is, that one of the base transceiver stations with which the mobile station is best able to communicate.
This invention was originally conceived to solve the problem of identifying geographical areas where communication between the fixed part of the system and mobile stations, or particular makes or models of mobile stations, is weak, for example where drop-out is a problem, so that the system may be modified, for example by the relocation or addition of base transceiver stations, so that the service provided by the system can be improved. However, it will be apparent from the following description that the invention has other uses.